This article is for an older version of CCC. You can find the latest version here.

We're happy to help you troubleshoot your bootability problems. Before you ask for help, please try the troubleshooting steps below. If you're having trouble with the steps or have run out of options, please let us know how far you got, or how far your Mac gets into the boot process.

If CCC's Cloning Coach didn't report any configuration concerns for your backup volume and you are having trouble booting from it, try the following troubleshooting steps (in order):

  1. If you are using an external hard drive enclosure, confirm with the enclosure vendor whether your enclosure should support booting your Mac. The bottom of this page has a list of related discussions that describe specific configurations that we've seen problems with in the past.
  2. Reboot your Mac holding down the Option key.
  3. Wait about 30 seconds to see if the backup volume appears. If your backup volume appears at this step and the boot process proceeds past the Apple logo, skip to the next section below.
  4. Detach, then reattach the backup volume's firewire or USB cable from/to your Mac and wait up to another 30 seconds.
  5. Shut down your Mac completely, then start it up holding down the Option key, waiting another 30 seconds for the volume to appear.
  6. Repeat the steps above, but using another interface (e.g. USB if you tried Firewire, Firewire if you already tried USB) and see if the volume appears. If you have multiple USB ports, try each port. If you are using a USB 3.0 enclosure, try using a USB 2.0 cable.
  7. If the hard drive enclosure is bus powered, try plugging in its DC power supply before starting up your Mac. Bus powered enclosures often take a bit longer to spin up or simply don't make themselves available that early in the boot process.
  8. Lastly, try resetting your Mac's parameter RAM. PRAM maintains settings related to starting up your Mac, and it's possible that invalid settings are interfering with your Mac's discovery of the external enclosure. To reset your PRAM, hold down Command+Option+P+R on startup. Hold down those keys until you hear the second startup chime. Release all but the Option key after you hear the second startup chime.

If the volume still won't boot, it's possible that the enclosure doesn't support booting your Mac. The Golden Litmus Test for bootability would be to install OS X directly onto the volume. If that fails to make the disk bootable, then it definitely isn't going to happen. Please report these enclosures to us so we can assemble a list of troublesome enclosures.

The backup volume starts to boot the Mac, but is slow or never gets to the Finder

There are several visual hints that can indicate how far your backup volume is getting in the startup process:

  1. Apple logo: The "booter" file was found and executed.
  2. Spinning progress indicator: The OS "kernel" was executed and now has control over the startup process. The kernel will load kernel extension caches, mount the startup disk, then execute "launchd" which kicks off all of the other system processes.
  3. Blue screen: The WindowServer has loaded, so the system is ready to start loading regular applications or the loginwindow.
  4. Loginwindow or your Desktop: The system has finished loading, and is ready for user interaction

If your backup volume showed up in the Option key startup disk selection screen, but doesn't display the Apple logo when you choose to start from it, then your Mac is having trouble finding the "booter" file on this volume. This can occur due to hard drive enclosure interference, due to filesystem corruption on the backup volume, or due to the volume being improperly "blessed" (blessing a volume stores certain information about the startup files in the volume's header, and your Mac uses that information to start the boot process).

  1. If you can rule out enclosure problems, use Disk Utility to repair any filesystem problems on the backup volume
  2. Run your backup task again
  3. Try booting from the backup volume again

If you see the universal "No access" symbol after selecting your startup disk, this indicates that the kernel cannot load the kernel extension cache, or that it cannot mount the startup disk. This could be due to trying to run an incompatible operating system on your Mac, or due to an extension conflict with the enclosure you are trying to boot from. We see this quite frequently when trying to boot from a USB 3.0 enclosure, especially on Macs that do not have native support for USB 3.0.

  • If you are booting a different Mac than what the backup volume was cloned from, try installing OS X directly onto the cloned volume while booted from the OS X Installer DVD or the Apple Recovery volume
  • If you're booting the same Mac from which you created the backup, try booting into Safe Boot mode (hold down the Shift key as you start your Mac).

If your Mac never progresses past the spinning progress indicator (below the Apple logo) or hangs at the blue screen while booting from the backup volume, there is probably a problem with some of the system files that are called early in the startup process. The system log on the backup volume can be very useful in troubleshooting these problems. To view the system log:

  1. Boot your Mac from its usual startup disk
  2. Choose "Go to folder" from the Finder's Go menu
  3. Type "/Volumes/Backup volume name/var/log" (no quotes, and substitute the actual name of the volume) and click the Go button
  4. Double-click on the system.log item in this folder

Look for any error messages, indications of crashes, etc., or simply attach the system.log file to a discussion on the Bombich Software Help Desk.

Configurations with which we have seen some problems